Wild rats are commensal animals whose natural
habitat is in and around human buildings: farms, cities, sewers,
garbage dumps. In cities, wild rats are more common in neighborhoods
of low socioeconomic status.

Wild rat bites are relatively rare, but their exact number cannot
be determined because bites are greatly under-reported. People of all
ages are bitten by urban wild rats, but the majority of rat-bite
patients tend to be children. Most bites happen at night while the
patient is sleeping. Rats tend to bite parts of the body that are
exposed during sleep, like hands and fingers.

Rat bites are usually not severe: most bites are simply washed and
the patient is immediately released. The infection rate of rat bites
is very low -- about 2%.

Very rarely, a rat may transmit a disease such as rat bite fever
or ratpox through a rat bite. Rats are not a rabies risk in the
United States.

Are wild rat bites
common?

It's difficult to estimate how common wild rat bites are, because
animal bites tend to be under-reported. Probably less than 10% of all
bites are brought in for medical care (Strassburg et al.
1981). Of bites that are brought in, one study found that only 41%
are reported to health authorities (Beck 1981). Even dog bites are
under-reported: in Pennsylvania, a study of children aged 4-18 years
found that the rate of dog bite was 36 times greater than the rate
reported to health authorities (Beck and Jones 1985).

Rat bites are greatly under-reported as well. Social Services
visits to the homes of rat-bite patients showed that the patients'
family members usually had unreported rat bites (Ordog et al.
1985).

In general, however, it appears that rat bites are relatively rare
even in areas where rats are common. A survey of 1,363 people in
Baltimore found that although nearly two-thirds of respondents (64%)
reported seeing rats in streets and alleys, only 6% reported seeing
rats inside residences, and only 1.2% had experienced any rodent bite
(rat or mouse) in their lifetime (Childs et al. 1991).

Hirshhorn and Hodge (1999) found that the incidence of rat bites
in Philadelphia was 2.12 bites per 100,000 people per year from 1974
through 1984, and 1.39 per 100,000 people per year from 1985 through
1996.

Childs et al. (1998) examined the environmental and social
characteristics of the home blocks of 514 patients that had been
bitten by rodents (81% of the bites were due to rats). The authors
found that most people who had been bitten lived in poor inner-city
neighborhoods. These high-risk neighborhoods were more crowded, had
more residences per block, a higher percentage of rental units, and
more vacant addresses than low-risk blocks. The populations tended to
have a high percentage of ethnic minorities (except Asians), a large
percentage of children and a low proportion of people over 65.

High-risk neighborhoods also tended to be near subways, waste
stations, railroads and parks, which are all a potential source of
refuge and food for Norway rats. However, living near noisy
transportation and waste stations may also be a characteristic of
less affluent neighborhoods (Childs et al. 1998).

Hirshhorn and Hodge (1999) studied 622 rat bite cases on record
in Philadelphia from 1974 to 1996. The study found that rat bites
primarily affected children age five and younger, with a range of
less than 5 to over 75 years of age.

Childs et al. (1998) found an older median age of 22
years with a range of under 1 year to 93 years.

Ordog et al. (1985) found that the average age of a bite
patient was10.8 years, with a range of 5 months to 42 years. The
majority (74%) of bite patients were under 15, while 45% percent
were under five years old.

Sallow examined rat bites in Baltimore between 1948 and 1952.
This study found that 60.5% of victims were under six years of
age. Infants of less than one year accounted for 24.5%.

Richter (1945) studied rat bites in Baltimore between 1939 and
1943. This study found that 60% of rat bite victims were less than
1 year of age.

Race

During 1974 to 1996, Hirshhorn and Hodge (1999) found
that 50% of rat bite victims were black, 28% were white, and 22%
were of Asian or Spanish origin. Blacks and Hispanics were
represented disporportinately as having a high risk of receiving a
rat bite. Between these two groups, Hispanics had an incidence
rate four times greater than blacks.

Socioeconomic status

More bites occur in neighborhoods with the highest
percentage of families living below the poverty line and the
highest percentage of unemployed people. There is a close
association between the incidence of rat bites and poverty
(Hirshhorn and Hodge 1999).

Infirmity and weakness

Ninety percent of Ordog's rat-bite patients were either
children, or had a physical or mental disability such as diabetes,
a psychiatric disorder, intoxication, or a prior wound (Ordog
et al. 1985).

Bitten person's location

All of Ordog's (1985) rat bites occurred in the patients'
own homes. Hirshhorn and Hodge (1999) found that 92% of bites
occured in the home (67% single family dwellings, 25% multiple
family dwellings), while the remaning 8% of bites occured in other
structures (e.g. research laboratories and schools).

Hirshhorn and Hodge (1999) found that 53% of rat bite victims
recorded between 1985 and 1996 (33% between 1974 and 1984) lived
in a residence that was in poor physical condition and had poor
sanitation ratings both inside and outside.

Hirshhorn and Hodge (1999) found that most bites (83%) occured
between midnight and 6 a.m.

Where on the body do rats bite?

Most bites were to extremities. This is because most
people are bitten at night while they are asleep. Rats tend to
bite the parts of the body that are exposed during sleep: the
face, arms and hands.

Ordog et al. (1985) found that 70% percent of rat bites
were to the upper extremeties: the arm, wrist, hand, or finger.
Eighteen percent were to the lower extremities of leg, thigh, or
buttocks. The remaining 14% percent of the bites were to the face.
Most of these bites were to areas of the body exposed while the
patient was asleep.

Childs et al. (1998) found that 59.8% of bites were to
the upper extremities of arm, wrist, hand or finger. Twenty-eight
percent were to the lower extremities of leg, foot, or toe, while
9.3% were to the head, face or neck. The remaining 2.4% were to
the body and trunk.

Hirshhorn and Hodge (1999) found that 48.3% of bites were to
the hand, 19.6% were to the head, 15% to the foot, and 9% to the
leg.

Richter (1945) found that 48% of bites were to the hands and
arms, 20% to the face, and 19% to the legs and feet.

Time of year

Hirshhorn and Hodge (1999) found that most bites (48%)
occur from May through August.

Type of wound

Sixty-one percent of the bites were single or multiple
punctures. Fourteen percent were lacerations (all less than < 1
cm), 12% were abrasions, 6% were ecchymoses (bleeding in the
skin), 5% were hematomas (bruise), and 2% were fractures (one
patient's fingertip was fractured). Twelve percent of patents
received wounds of multiple types (Ordog et al. 1985).

Treatment and infection rate

Most rat bites were not severe. Childs et al.
(1998) found that most bites were simply washed and 98% of 514
patients were immediately released. Ordog et al. (1985)
examined 50 rat bite patients, and only one patient (2%) developed
a bacterial infection that required antibiotics.

When bite wounds were swabbed, only 30% of the wounds had a
positive bacterial culture. Of these, 43% were Staphylococcus
epidermidis. The remainder were Bacillus subtillus,
diphtheroids, and alpha hemolytic streptococcus (Ordog et
al. 1985).

Victim profile summary

The victim of a rat bite is mostly likely to be a child
of either sex of less than five years of age, often nonwhite. The
victim is usually bitten on the face or arms while asleep at home
in the bedroom some time between midnight and 8 a.m. Poor, younger
children are bitten by rats more frequently than adults (Hirshhorn
and Hodge 1999).

Diseases transmitted by rat
bite

Diseases transmitted by rat bite are rare. In two surveys of 514
and 50 rat bite patients, no patient contracted a disease from the
bite (Childs et al. 1998, Ordog et al. 1985).

Very rarely, a rat may transmit rat
bite fever (Graves and Janda 2001, Grude 2001, Schuurman et
al. 1998, Hagelskjaer et al. 1998, Hockman et al.
2000, Weber 1982) or ratpox/cowpox (Marennnikova et al 1988,
Postma et al. 1991). Rabies
from rats is very rare and has never been documented in the United
States. However, a handful of cases of rabies from a rat bite have
been recorded in Poland (Zmudziñski and Smreczak 1995,
described in Wincewicz 2002), Israel (Gdalevich et al. 2000),
Thailand (Kamoltham et al. 2002) and Surinam (Verlinde et
al 1975).